Lord Prescott, the former deputy prime minister, is to make constitutional history by resigning from the Privy Council in protest over its "highly political" role in the debate surrounding press regulation. This is believed to be the first time a member of the prestigious body, set up to advise the monarch, has resigned on a point of principle.

The shock move reflects Prescott's deep anger at the way plans to reform press regulation are, he believes, being watered down following intense lobbying by several newspaper groups.

His decision to quit the position with immediate effect means he will drop the "right honorable" title.

The unprecedented move will have constitutional experts reaching for their history books. Disgraced ministers John Profumo, John Stonehouse and Jonathan Aitken all resigned the right honorable title. More recently, Elliot Morley was stripped of the status following his conviction over the MPs' expenses scandal. Chris Huhne resigned last year after admitting to having perverted the course of justice in 2003.

But Prescott's resignation is a political gambit designed to reignite the debate over the future of press regulation in the wake of the phone-hacking scandal that led to the closure of the News of the World in 2011.

His decision to quit, revealed in a letter to the clerk of the council, Richard Tilbrook, posted on Friday and seen by the Observer, is likely to overshadow its meeting on Wednesday. In the letter, Prescott says he is resigning because he believes the government now favours the rival royal charter proposal backed by Pressbof, the body representing most newspaper and magazine publishers.

This is despite the prime minister, David Cameron, telling parliament last week that the Pressbof proposals had "serious shortcomings".

But Prescott writes: "After a number of statements made to parliament this week, including one from the prime minister, it is clear that the government intends to give priority in consideration to the press industry's PressBof charter rather than one agreed unanimously by parliamentarians."

He adds: "I believe that the Privy Council is being used in a highly political way to block real and much-needed press regulation. I cannot stand by and be party to this."

Critics of the Pressbof proposals believe they do not go far enough in ensuring a robust and independent oversight of the press.

In his column in this week's Sunday Mirror, Prescott expresses his concerns that the issue of press regulation will drag on until the next general election. He also suggests that the Privy Council's apparently political role in the affair threatens to drag the monarchy into a possible conflict with parliament.

Prescott explains in his letter that, "having examined all the details, including legal advice, I am of the view that a combination of government ministers and press barons have combined to delay the implementation of parliament's royal charter, by procrastination and half-truths."

The damning claims of collusion will be fiercely rejected by the government. The culture spokesman, Lord Gardiner, told parliament last week that it was right that the rival Pressbof proposal was subjected to "due process".

But Prescott said: "The Privy Council must put parliament and the victims' views first, before the press, when considering legislation."